Colloidal lithography using silica particles: improved particle distribution and tunable wetting properties.

Colloidal lithography rests on the adhesion of colloids in a relatively ordered pattern on a charged surface owing to electrostatic interactions. However, due to capillary forces, the colloids tend to form aggregates during the drying process. These capillary forces are especially strong for large hydrophilic particles. In this paper, different experimental approaches are explored to limit the aggregation of large (500 nm) silica particles deposited on glass substrates that were previously treated with polyallylamine (PAH), a polycation. These approaches consist in the addition of smaller colloids between the large ones, or of a layer of macromolecules (PAH or albumin) on top of the deposit. Scanning electron microscopy observations show that the addition of PAH and even better of albumin on top of the adherent colloids efficiently limits the formation of aggregates. Interestingly, the water contact angle of the surface obtained after silica colloid deposition and albumin adsorption is very high (~95°), while very hydrophilic surfaces are obtained after calcination. This is discussed in light of the Wenzel and Cassie-Baxter models. In conclusion, the proposed method allows a nanoscale topographic pattern with tunable wettability to be created on large surface areas using a soft and inexpensive technique.